peterleroux wrote:
First thing I would check is how well the strings are grounded- do you have a wire from the bridge to your grounding point, and if so, is it making good contact with the bridge?
+1
I had a funny one on a 70's bass - the pickup had a ground (connected) but everytime I touched the cover I got a hum - sounded like a grounding issue - popped a ground onto the cover and fixed!
Can also use a continuity tester on a multimeter between all the grounding points (bridge to back of pots, jack, etc..) to double check that the ground is getting everywhere it should.